The present invention relates to multi-pane thermally insulating construction particularly adopted for use in buildings and, more particularly, thermally insulating windows.
For a number of years, and particularly since the energy crisis in the early 1970's, persons in the building construction industry throughout the world have been working on improving the thermal insulating quality of windows since this is one of the areas in a building where high thermal losses occur. Therefore, the building industry in general, particularly in exceedingly hot or cold climates, has turned to double glazed, thermally insulating windows. These windows have been modified in recent years in an effort to further improve insulating efficiency and prolong the effective life of the windows.
One modification in thermally insulating windows is the development of "Low E" glass wherein the surface of the glass is treated so that infared rays are reflected while visible light can pass through. Other modifications include a transparent plastic membrane with infared reflecting properties. But probably the most important modification has been the replacement of air in the compartment formed by two spaced transparent panels, glass or plastic, with an inert gas. Among inert gases argon is the preferred gas. By using argon, significant improvements in thermal insulating properties have been achieved.
A significant problem in prolonging the life of argon gas filled thermally insulating windows is the loss of the gas through the elastomeric seals formed between the inner edge margins of the panels forming the compartment containing the argon gas. The prior art elastomeric sealants have allowed the gas to diffuse through the seal which, within two or three years, cause significant loss of the argon gas and the thermal insulating qualities of the thermally insulating windows. The present invention provides seals which surprisingly significantly reduce the loss of argon. As a matter of fact, the thermal insulating construction of the present invention utilizing the seals disclosed herein increases the life of the multi-pane thermally insulating construction two fold.
The seals of the present invention are formed by using thioether mercaptan terminated disulfide liquid polymer compositions which cure to solid elastomers and surprisingly exhibit substantially decreased permeability to argon gas in addition to having other desirable properties including high tensile strength and excellent resistance to ultraviolet light. The polymer compositions of the present invention are produced through the chemical modification of standard polysulfide liquid polymers with alkyl thioether dithiols of from 4 to 20 carbon atoms.
The thioether mercaptan terminated disulfide liquid polymer compositions used to produce the seals of the present invention are disclosed and claimed in co-pending application Ser. No. 768,402, filed Aug. 21, 1985, now U.S. Pat. No. 4,623,711, said co-pending application having the same assignee as the instant application. However, said copending application also discloses and claims many polymer compositions other than those used to provide the seals in the thermally insulating windows of the present invention. These other polymer compositions disclosed in the co-pending application do not possess the very unique property of very low permeability to argon gas which the thioether mercaptan terminated disulfide liquid polymer compositions disclosed herein have. This unique property allows the production of multi-pane thermally insulating constructions having an exceedingly long life (more than double the life of the prior art multi-pane thermally insulated constructions).
The most frequently used liquid polymers in sealants for argon filled multi-pane windows are "Thiokol" polysulfide liquid polymers such as those disclosed in U.S. Pat. No. 2,466,963 which issued in 1949. Typically, polysulfide polymers prepared in accordance with the teachings of this earlier patent have molecular weights on the order of about 2000 to about 8000 and are viscous liquids having viscosities ranging from about 1500 to about 150,000 centipoise. These polymers are formed of repeating units of diethyl formal disulfide with terminal mercaptan groups (hereinafter referred to as "diethyl formal mercaptan terminated polysulfides"). When such polymers are cured, they form hardened rubber-like solids exhibiting a number of desireable properties including resistance to water, ozone and sunlight. Additionally, these prior art polymers are relatively impermeable to inert gasses. As a result, prior art cured diethyl formal mercaptan terminated polysulfides have been widely used in sealants for multi-pane thermally insulating windows.
In multi-pne thermally insulating windows it is essential that the compartments containing the argon gas are effectively and reliably sealed against escape of the argon gas. It is also important that the sealants used in multi-pane thermally insulating windows are useful over a broad temperature range encountered in extremely cold climates and in extremely hot climates. It is also critical that such seals not be degraded by ozone or ultraviolet light. The prior art polysulfide sealants have been somewhat effective at preventing argon gas loss in multi-pane thermally insulating windows. But there certainly is a distinct need in the art to improve upon these prior art elastomeric compositions by decreasing the permeability to argon gas. If the escape of argon gas through difusion could be substantially decreased, this would mean that such multi-pane thermally insulating windows would have their useful life increased by many years.
Accordingly, it is the principal object of the present invention to provide a multi-pane thermally insulating construction having compartments filled with argon gas, said compartments being formed by two or more spaced panes, the inner edges of the panes being effectively sealed with a solid elastomer which substantially reduces the difusion loss of argon gas.
Another and further object of the present invention is to disclose and provide a method for making such multi-pane thermally insulating constructions which significantly reduce the loss of argon gas.
These and other objects of the present invention are achieved by the present invention by providing seals in multi-pane thermally insulating constructions, such as windows, in which the seals of such constructions are formed by thioether mercaptan terminated disulfide liquid polymer compositions which, when cured, exhibit significantly reduced argon gas permeability without sacrificing strength, resistance to environmental attack, or adhesion.